Gun choke



Jan. 26, i965 A. Y. GRAHN 3,166,865

GUN cHoKE Filed sept. 3o, 196s ma @am ATTORNEYS United States Patent Office 3,165,855 Patented Jan. 26, 1965 3,16t3,865 GUN CHOKE Ame Y. Grahn, Granby, Conn., assignor to The Poly Choke Company, incorporated, Hartford, Conn., a corporation of Connecticut Filed Sept. 3G, 1963, Ser. No. 312,645 7 Claims. (Cl. L12-79) This invention relates to a choking mechanism for rearms and, more particularly, to the novel construction of a gun choke for a shotgun or the like. The invention is more specifically directed to an adjustable choke which may be adjusted to varying degrees of muzzle constriction at the end of the gun barrel. The device disclosed herein is an improvement over prior known devices and is of the same general type as that shown in United States Patent 2,968,111 issued to H. W. Steane on January 7, 1961, assigned to a common assignee.

As described in the aforementioned patent, an adjustable shotgun choke, attached to the muzzle end of a shotgun barrel, will control the shot pattern and be capable of d-irecting 75 %-80% of any shot load within a thirty inch circle at any normal shotgun range. (Normal shotgun range is 15 t-o 5() yards.) The purpose of the shotgun choke is to provide the shooter with the same shot pattern regardless of the range to the target. Adjustment of the shot pattern to shoot different ranges is accomplished by adjustment of the choke sleeve. The shooter may thus select the desired shot pattern for particular shooting activities. Since shotgun sports have wide requirements with regard to range, the adjustable shotgun choke allows the shooter to participate in all activities with only one shotgun, whereas, without a means of adjusting the choke, the shooter would require a gun with several different barrels. For example: A duck hunter requires a 75% to 80% pattern at 40 yards while a Skeet shooter requires the same performance at 2() yards; additionally, the upland game hunter must have the required pattern at 30 yards. These different requirements are all met by suitable adjustment of the choke sleeve using the appropriate settings.

Utilising the choke described and claimed in aforementioned US. Patent 2,968,111, an improved choke was constructed which would provide a more uniform pattern than was provided by previous gun chokes. This was accomplished by adjusting the movable sleeve member threadedly engaging the shell member aflixed to the gun barrel along two axially-spaced, circumferential areas. Furthermore, the langles of the contact areas and the thread lead were selected so that adjustment from the full open to the full choke position could be effected by a single rotation of the sleeve relative to the shell.

As may be readily understood, when a shotgun is discharged and the shot travels through the barrel, some of the shot will strike the inner surfaces of the choke, thereby causing shock to the choke, -a dissipation of energy, a distortion of the shot and a disorientation of the shot pattern. These occurrences are undesirable but are considered to be inherent inthe nature of the choking mechanism. Naturally, these undesirable effects are maximized at the full choke position. The invention herein is adapted to minimize these undesirable effects.

Accordingly, it is an `object of the present invention to provide an improved gun choke which will reduceV the impact' or shock to the gun and choke mechanism upon discharge.

Another object of the invention is to provide an improved gun choke which will reduce mutilation or distortion of -that portion of the shot coming in contact with the inner walls of the choke.

Still another object of the invention is to provide an improved choke which will reduce the disorientation of the shot pattern caused by contact of the shot with the inner walls of the choke.

Still other objects and advantages of the invention will in part be obvious and Iwill in part be apparent from the specification.

Generally speaking, in accordance with the invention, a gun choke is fabricated from two elements, one element being the shell and the other the sleeve. The shell element is secured to the end of a gun barrel and the sleeve threadedly engages the shell to provide for choke adjustment when the sleeve is rotated with respect to the shell. The shell comprises la plurality of segments adapted to be deflected inwardly by the camming of interior surfaces of the sleeve against exterior surfaces of the shell. The surfaces on the segments lie intermediate the ends of the shell and are adjacent or proximate to the plane which delineates the body of the shell from the segments. Substantially mating surfaces on the inside of the sleeve are provided. The outer ends of lthe segments are so constructed and arranged that they .are freely received within the sleeve. In other words, the outer ends of the segments do not contact any portion of the interior surface of the sleeve regardless of the choke setting.

The invention accordingly .comprises an article of manufacture possessing the features, properties, and the relation of elements which will be exemplified in the article hereinafter described, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the invention, reference is had to .the following description taken in connection with the accompanying drawing, in which:

FIG. l is a longitudinal, sectional view of a choke constructed in accordance with the present invention, the choke being mounted .to the end of a gun barrel andadjusted to the full open position; v

FIG. 2 is a partial sectional view, similar to FIG. 1, but showing the article adjusted to the full choke position;

FIG. 3 is a partial sectional view of the shell portion of the novel choke; and

FIG. 4 is a partial sectional view of the sleeve portion of the novel choke.

Referring first to FlG. 3, the choke shell, indicated generally at 11, comprises a body portion 12 and a plurality of axially or longitudinally-extending segments 13 separated by a plurality of slots 14. Body 12 is provided with an aperture 15 adapted to receive therein the muzzle end of the gun. A series of threads 16 are carried by a portion of the external surface of body 12 for engagement with the sleeve as will be hereafter described. Although shell 11 is delineated by a body portion 12 and segments 13, the shell is preferably constructed as a single unit, with the segments being defined by the slots 14 extending parallel to the central `axis of the shell. A cylindrical discharge chamber 17 is defined Iby the inne-r cylindrical surfaces 18 of the segments, chamber 17 communicating with aperture 15. As will be seen hereafter, the diameter of chamber 17 is the same as the diameter of the gun barrel at :the muzzle end.

The diameter of the peripheral surfaces 19 of the segments is a maximum proximate t-o the body portion of the shell and is indicated las D1. 'From the forward edge of surfaces 19, the segments taper to form bearing surfaces 21 which extend toward the outer end of the segments, While not so limited, it has been found, in the preferred embodiment, that the `desired results are obtained when bearing surfaces 21 taper `at an angle of 5. From the forward edge of the tapered bearing surfaces 21, the peripheral surfaces 22 extend substantially parallel to the central axis of the shell toward the outer ends of the segments. The outer ends of the peripheral surfaces terminate in tapered surfaces 23 which may taper at yan l angle of approximately Referring now to FIG. 4, a sleeve indicated generally at 31 is adapted to lit `over and engage shell 11 in a manner to be hereafter described. The cylindrical exterior surface of sleeve 31'may have any suitable configuration and a portion thereof will preferably be knurled so that the sleeve may be manually rotated with ease. A cylindrical aperture passes longitudinally through sleeve 31 and will now be described. The inner end of sleeve 31 is provided with a cylindrical opening having a clearance diameter 32 which is of sufficient size .to clear the maximum diameter of shell 11. Adjacent cylindrical opening 32 within the sleeve is a threaded portion 33 adapted to mate with the thread 16 on shell 11. Threaded portion 33 extends 4for a substantial. length within the sleeve. It will be noted from the preferred embodiment disclosed and claimed in Patent 2,968,111 that a pitch of 24 threads to the inch was demonstrated to be satisfactory. Threaded portion 33and threads 16 may have this pitch or any other suitable pitch. Proximate to threaded portion 33 is a cylindrical segment 34 which is substantially parallel to the central axis of the sleeve and has an inner diameter indicated as D2. In the preferred embodiment, it has been found desirable to make the inside diameter D2 of cylindrical segment 34 smaller than the youtside diameter D1 of peripheral surfaces 19 on the shell, thereby providing an interference fit. In one embodiment of the choke which was successfully tested, lan interference lit of .005 proved satisfactory. I

From cylindrical segment 34, the internal aperture in sleeve 31 tapers at `an angle of approximately 7, defining an internal circumferential bearing surface 35. A straight cylindrical segment 36 extends from tapered bearing surface 35 and the aperture is thereafter defined by a tapered segment 37 which may taper at an angle of approximately 17. The final portion of the aperture through sleeve 31 is determined by a straight cylindrical segment 38 wh-ich extends through the outer end of sleeve 31.

The elements are assembled as shown in FIG. 1. The choke is adapted to be mounted to the muzzle end 41 of a gun barrel 42. In the embodiment shown, the gun barrel is undercut along a length of .the outer peripheral surface adjacent Vthe muzzle end, the undercut being indicated as 43 and is adapted to tightly engage aperture 15 in the shell. In the preferred embodiment shown, the shell will be brazed tothe gun barrel along the mating surfaces 15 and 43. Of course, any suitable means can be utilized to mount the shell to the gun barrel, threaded means being shown in aforementioned Patent 2,968,111.

Sleeve 31 is mounted over shell 11 with threaded portion 33 threadedly engaging thread 16. Because of the interference lit between cylindrical segment 34 and the peripheral surfaces 19 of the segments 13, the segments will be deected inwardly thereby pre-stressing them to a degree dependent upon the extent of the interference iit. Of course, it will be understood that the segments may deliect due to the resiliency of the shell material and the plurality of slots 14 delineating the segments.

In FIG. 1, sleeve 31 is depicted as being screwed onto shell 11 to the full open position. In other words, when assembled the sleeve will be screwed onto the shell by at least the amount shown in FIG. 1. Suitable marking or indicia ymay be carried -on the shell and the sleeve to indicate this position. In the full open position, it will be noted that bearing surfaces 21 on the shell engage t-he bearing surface 35 forming a portion of the aperture through the sleeve. The engagement of these surfaces also causes radially inward deflection of segments 13, thereby assuring that the forward portion of the outside surfaces of the segments do not contact the inner surfaces of the sleeve which they oppose. Specifically, peripheral surfaces 22 are spaced from the inner surface of straight cylindrical segment 36 by `a preselected amount. A spacing of .005l has been found satisfactory. Also, tapered surfaces 23 are spaced from the inner surface of tapered segment 37 so that no portion of the outer peripheries of the segments 13 forward of bearing surfaces 21 Contact any of the inner'surfaces of sleeve 31.

Since, during initial assembly of sleeve 31 on shell 11 to the full open position, the segments will be inwardly deflected due to the interference fit and the engagement of bearing surfaces 21 with bearing surface 35, a semichoke position will be attained by the segments. To eliminate this, while maintaining the pre-stressing of the segments caused by the interference fit, the bore of the shell is reamed slightly to substantially straighten chamber 17 in the full open position. Note that when the shell is assembled, chamber 17 aligns with the discharge openface V35 rides on bearing surfaces 21, thereby providing a camming action due to the slope of the inclined surfaces.

. This camming action causes inward deflection of each of segments 13 thereby decreasing the size of chamber 17 defined by the segments. It will be readily seen that the cross-sectional sizeof the chamber will be a minimum 'at the outer end of the shell. The inward deliection of segments 13 also assure that peripheral surfaces 22 and tapered ysurfaces 23 remain out of contact with the proximate interior surfaces on sleeve 31. Note also that the inward deflection of segments 13 tend to reduce the size of slots 14 particularly at the outer ends thereof. However, the width of the slots is preferably selected so that adjacent segments will not touch one another, even at the full choke position.

Of course, it will be understood that intermediate amounts of choke may be attained by rotating sleeve 31 relative to the shell by varying degrees within the limit of adjustment. Suitable indicia may be scribed on the shell and the sleeve `to indicate the various positions or degrees of choke such as those indicated in aforementioned Patent 2,968,111.

Once the construction of the improved choke is known, its advantageous operational features readily 'become apparent. When a shotgun shell is fired, a large number of small pieces of shot, usually lead shot, travel down the barrel and pass through the choke prior t-o discharge. Since the choke restricts the discharge aperture as compared with the bore of the gun barrel, at least some of the shot will impinge upon and be deliected by the inner `surfaces of the choke, and particularly the inner surfaces 1S, of the segments. While this provides means for controlling the shot pattern, cer-tain of the shot impinging upon the inner surfaces of the choke become mutilated and are deflected thereby tending to disorient the shot pattern. Furthermore, over a period ofV time, the shot can do damage to the choke and the gun due to the shock of the shot against the walls of the choke.

In previous chokes, the segments were supported against the inner surface of the sleeve to prevent deflection. In FIG. 1 of Patent 2,968,111, it may readily be seen that the segments are supported at their outer ends as well as intermediate their ends. By providing the clearance heretofore described and shown in FIGS. 1 and 2, the outer ends of the segments .are free to deflect under the force of shot impinging thereon. By permitting deflection of the outer ends of the segment, it has been found that the resiliency tends toy prevent mutilization of the shot which strikes the inner surfaces of the ysegments and also reduces deiiection of the shot thereby tending to prevent disorientation yof the shot pattern. Furthermore, the resiliency of the segments absorbs Vsorne of the force of impact thereby reducing the damage done to the choke and gun over a period of time. It is preferred that the spacing of peripheral surfac 22 and tapered surfaces 23 from the interior segments 36 and 37 on the sleeve is sufficient to prevent contact, even during deflection of the segments caused by the tiring of shot through the choke.

It should also be noted that the outermost area of support of the segments is the engagement of bearing surfaces 21 with bearing surfaces 35. The severest condition of shock land deflection occurs at the full choke position since this position provides maximum restriction for the discharged shot. In the severest condition, it is preferable to give maximum support to the segments without reducing their resiliency. For this reason, the angle of incline or taper of bearing surfaces 21 is less, by a few degrees, than the incline of bearing surfaces 35. In this way, as segments 13 are deected inwardly, the angle of bearing surfaces 21 will increase thereby closely approaching or equaling the angle of bearing surfaces 35. When the angles are approximately equal, maximum contact between the surfaces will be attained. The drawing clearly shows that greater contact of surfaces is effected at the full choke position of FIG. 2 than at the full open position of FIG. l.

In the ful-l choke position, wherein maximum deflection of segments 13 is provided, the bending stresses placed on the segments by the deflection thereof increases the shockabsorbing capacity. Conversely, the shock-absorbing capacity would be at a minimum in the full open position. However, it is not desirable, even in the full open position, to have the segments freely supported and, therefore, a certain amount of pre-stress is placed thereon. This is effected by the interference fit between the shell and the sleeve as heretofore described. Of course, this interference t will cause deflection of the segments and, for this reason, the bore of the shell is reamed at the full open position after the shell and sleeve have been initially assembled.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are eiciently attained and, since certain changes may be made in the above article without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

What is claimed is:

l. An adjustable choke for a gun barrel comprising:

(a) a tubular cylindrical shell element adapted to be secured at its rear end to the muzzle end of a gun barrel,

(i) said shell element havin-g a plurality of longitudinal slots opening through its forward end to divide its forward portion into spaced segments resiliently displaceable inwardly,

(ii) said segments having an annular series of tapering shoulders spaced from the forward ends of said segments, said annular shoulders Ibeing inclined rearwardly, and

(b) a sleeve embracing said shell element and threaded-ly connected thereto for movement longitudinally thereof,

(i) said sleeve having a complementary tapering annular shoulder thereon to engage the shoulders of said segments and displace said segments inwardly to constn'ct the effective size of the tubular opening therethrough.

(ii) said sleeve having an annular portion spaced from the exterior surfaces of said segments for- Ward of the tapering shoulders whereby contact of said segments with said sleeve forward of the tapering shoulders is prevented.

2. An adjustable choke for a gun barrel comprising:

(a) ya tubular cylindrical shell element adapted to be secured at its rear end to the muzzle end of a gun barrel,

(i) said shell element having a plurality of longitudinal s-lots opening through its forward end to divide its forward portion into spaced segments resiliently displaceable inwardly,

(ii) said segments having an annular series of tapering shoulders spaced from the forward ends of said segments, said annular shoulders being inclined rearwardly,

(iii) said segments also having an annular series of substantially cylindrical surfaces extending rearwardly from the terminus of said rearwardly inclined annular shoulders, and

(b) a sleeve embracing said shell element and threadedly connected thereto for movement longitudinally thereof, 4

(i) said sleeve having a complementary tapering annular shoulder thereon to engage the shoulders of said segments and displace said segments inwardly,

(ii) said sleeve also having a complementary cylindrical annular surface to engage t-he substantially cylindrical surface of said segments,

(iii) said sleeve bein-g further provided with an .annular portion spaced from the exterior surfaces of said segments forward of the tapering shoulders whereby the contact of said segments with said sleeve forward of the tapering shoulders is prevented.

3. The structure defined in claim 2 wherein the outside diameter of said substantially .cylindrical surfaces is greater than the inside diameter of the complementary surface of said sleeve.

4. The structure dened in claim 1 wherein said annular series of tapering shoulders make an angle of 5 with the cent-ral axis of the tubular cylindrical shell element and the angle of taper of the annular shoulder on said sleeve :is greater than 5, said angle being selected to provide maximum contact of said complementary tapering shoulders when said choke is adjusted to the full choke position.

5. The structure de-ned in claim 2 wherein the outside diameter .of the substantial-ly cylindrical surfaces of said segment is greater than the complementary surface of said sleeve by the amount of .005 inch.

6. An adjustable choke for a gun barrel comprising, a tubular cylindrical shell element adapted to be secured at its rear end to the muzzle end of a gun barrel, said shell element having a plurality of longitudinal slots opening through its forward end to divide its forward portion into spaced segments resiliently displaceable inwardly, said shell element having a threaded portion on an external surface thereof rearward the terminus of said longitudinal slots, said segments having an annular series of tapering shoulders spaced from the forward ends of said segments, said annular shoulders being inclined rearwardly, said segments having substantially cylindrical surfaces extending rearwardly from the terminus of said tapering shoulders, and a sleeve embracing said shell element and having a threaded internal portion threadedly engaging the threaded portion of said shell element, said sleeve being rotatable relative to said shell element for longitudinal movement of said sleeve relative to said shell element, said sleeve having a complementary tapering annular shoulder thereon to engage the shoulders of said segments, and a complementary cylindricalsurface thereon to engage the cylindrical surface of said segments, the engagement of said surfaces being effective to displace said segments inwardly to constrict the effective size of the tubular opening therethrough, rotation of said sleeve relative to said shell element controlling the amount of 7 8 constriction, said sleeve also having an annular pontion 7. The structure dened in claim 6 wherein the outs'paced from the exterior surfaces Vf said segments forside diameter of said cylindrical surfaces of said shell ele- Ward of the tapering Shoulders whereby `Contat of Said ment 1s greater than the complementary surface on said sleeve whereby preloading of said segments is elected segments with said sleeve forward `of the tapering shoulupon` lmimal assembly of said sleeve andYshel-l element.

ders is prevented throughout the usable range of adjust- 5 ment of said sleeve relative to said shell. Y f No references cited. 

1. AN ADJUSTABLE CHOKE FOR A GUN BARREL COMPRISING: (A) A TUBULAR CYLINDRICAL SHELL ELEMENT ADAPTED TO BE SECURED AT ITS REAR TO THE NOZZLE END OF A GUN BARREL, (I) SAID SHELL ELEMENT HAVING A PLURALITY OF LONGITUDINAL SLOTS OPENING THROUGH ITS FORWARD END TO DIVIDE ITS FORWARD PORTION INTO SPACED SEGMENTS RESILIENTLY DISPLACEABLE INWARDLY, (II) SAID SEGMENTS HAVING AN ANNULAR SERIES OF TAPERING SHOULDERS SPACED FROM THE FORWARD ENDS OF SAID SEGMENTS, SAID ANNULAR SHOULDERS BEING INCLINED REARWARDLY, AND (B) A SLEEVE EMBRACING SAID SHELL ELEMENT AND THREADEDLY CONNECTED THERETO FOR MOVEMENT LONGITUDIANALLY THEREOF, 